Ok I filled my '97 3.0 extended aerostar back up today with about a half a tank. It had traveled 211 miles and took about 13.4 gallons to top it off which equates to about 15-16 mpg. I had topped it off previously on its trip home from the former owner. The 211 miles were right about half highway and half around town miles locally. I've been driving it easy with a light foot both on the highway and around town. The 3.0 is supposed to get about 23 highway and maybe 16 city, so using a little algebra I figured it should have used about 11.2 gallons, instead of the 13.4. The tires are hard and inflated properly, the brakes were inspected and found to be properly adjusted and not dragging or anything. So it's just a little disappointing, I was hoping for better. But this thing is 11 years old and I don't think it's ever been tuned up or tweaked with under the hood. But it's only got 28K original miles, I figured all the emission/ECU sensors, spark plugs, wires, distributor cap etc should all still be good. What do you guys think? Is there anything I should check that would be easy/obvious? I've heard changing spark plugs is a real beetch on this thing, and from what I can see it is. Don't want to waste my time doing something that doesn't need to be done yet, especially if it's a tough, hunched back/knucklebusting job in that cramped engine compartment!

I have an OBD 2 reader for my PC, maybe I'll scan the codes and see what I find. Any help or hints in the meantime would be appreciated.

 

what work beside the IM gaskets has been done since you put it back on the road?

start with a combustion chamber/ring pack soak cleaning.
hot engine. run a qt of tap water thru 1/8" tube in thru hole in TB plate at 2k rpm.
take out on freeway and run 10 miles.

then run a can of Berryman's B12 or Seafoam using the same technique except shut off engine when can empty and let set 2 hours. out to freeway for another hard run.

follow up with a can of above fuel system cleaner in 1/2 tank of gas.

run a least 5 tanks of gas thru before averaging your fuel mileage. 1/2 tank is not reliable. we are still on high ethanol winter mix fuel, aka junke gas.

 

96 - I haven't replaced the intake manifold gaskets. The only thing I've done to the motor is flush the cooling system and replace the air filter. The van is like newish under the hood. Do you think this thing could be carboned up or something? Not sure why it would be unless it's been driven very gingerly on short trips and has cold plugs. And what fuel system cleaner would you recommend? Berryman's or seafoam? Thanks for your help, I've been reading a lot of your posts and the information you share with everyone is outstanding. Really appreciate you taking the time to help!

 

Seafoam and Berrymans are both equally great products and I have used both. So use whichever one you can find the easiest.

As for millage, do what '96 has suggested. (along with running codes.)

Just because it is low millage does not mean all of the parts are like new. Age and temperature conditions affect some of those parts. Your O2 could be rusted/carboned and is switching slower than normal, your plugs could be carbon fouled, your plug wires might be cracked/rusted inside causing higher resistance. MAF sensor could use a good cleaning, check for rust/buildup on the wire.

That is all I can think of off the top of my head. Good luck!

 

Since you replaced the air filter lately, could it be that you forgot to plug the MAF back in? Also, if you took the hose clamp off, it may be leaking through there too.

 

93 - They have berryman's B12 and sea foam at advance auto, and the berryman's was MUCH cheaper. Like $2 a small can vs $8 for the sea foam. So since they seem to be comparable I bought two cans of the B12 and dumped it in the tank (which is full) for a start. The other stuff you mentioned I've thought about, but kinda dreading having to go in and change out plugs/wires/cap and all that. Is there a smart way to do this, or is it just reach and strain all the way?? And in a nutshell how do you clean the MAF?

copper - Good questions. I almost did leave the MAF unplugged, but I caught myself and plugged it in when I was finished. Also, I did tighten the flange clamp too. However, I did notice about 40 miles ago that the crankcase breather "T" fitting on the plastic intake runner was not connected to the breather tube. In fact the whole breather tube was missing! Some bonehead must have removed it and failed to reinstall it somewhere along the line. I've since installed a rubber vent tube between the T and a vent at the base of the oil filler tube. Is that the right place to put it? And do I need to install a PCV valve inline on the tube? I'm guessing yes. But to return to the low mileage, could a significant air leak (like that caused by a missing crankcase vent tube) after the MAF cause bad mileage? I would think it would make it run leaner because it would "trick" the MAF into thinking less air is going into the motor and thereby set a lower fuel injection schedule. But I dunno, maybe the O2 sensor would compensate and reset the enrichment schedule higher?

 

Also the timing may not be correct, and the Coolant Temp Sensor may be corroded. You should change the coolant too, since it gets old and starts causing rust if you don't replace it.


The missing link will cause bad gas mileage. The computer uses the MAF to determine how much air is going into the engine. This effect not only how much fuel it injects, but also the timing strategy. The O2 sensor will detect the problem to some degree, but the whole speed density schedule will be off. Fix the leak, the mileage should improve at least slightly, but probably significantly.

 

If that tube is missing, there is your mystery. Yes, you need that tube between the oil filler and the air hose. The PCV is connected elsewhere, not there.

 

On the 4 liter engines, the the PCV valve is on the driver's side, under the upper intake manifold. I think the vent tube going between the oil filler tube and the intake is just that, a hollow tube. Again, this is on the 4 liter engine.

You can use something like Jetspray Gumout to clean your MAF sensor, but go easy on the trigger, as the spray pressure is pretty high. Just carefully spray through the couple of coils of wires in the sensor.

By the way, if your engine uses a MAF sensor, it will not have a speed-density algorithm for setting air/fuel ratio. But unmetered air getting into the engine will make it run too lean. This is where the S-D system has a minor advantage over MAF; the air pressure is measured in the intake manifold.